Effect of co-medications on paritaprevir, ritonavir, ombitasvir, dasabuvir and ribavirin pharmacokinetics: analysis of data from seven Phase II/III trials

Clinical Pharmacokinetics of Paritaprevir

Paritaprevir is a potent hepatitis C virus (HCV) nonstructural (NS) protein 3/4A protease inhibitor that is used in combination with other direct-acting antivirals (DAAs) for the treatment of chronic HCV infection. Paritaprevir is primarily metabolized by cytochrome P450 (CYP) 3A4 and is administered with a low dose of ritonavir to achieve drug concentrations suitable for once-daily dosing. Coadministration of paritaprevir with ritonavir increases the half-life of single-dose paritaprevir from approximately 3 h to 5-8 h, doubles the time to maximum plasma concentration (T _max) from 2.3 to 4.7 h, and increases exposures 30-fold for maximum observed plasma concentration (C _max), 50-fold for area under the plasma concentration-time curve (AUC), and >300-fold for trough concentration (C ₂₄). Paritaprevir displays highly variable, nonlinear pharmacokinetics, with C _max and AUC increasing in a greater than dose proportional manner when administered with or without ritonavir. In the presence of ritonavir, paritaprevir is excreted mostly unchanged in feces via biliary excretion. Paritaprevir exposures are higher in Japanese subjects compared with Caucasian subjects; however, no dose adjustment is needed for Japanese patients as the higher exposures are safe and well tolerated. The pharmacokinetic characteristics of paritaprevir are similar between healthy subjects and HCV-infected patients, and are not appreciably altered by mild or moderate hepatic impairment or mild, moderate, or severe renal impairment, including those on dialysis. Paritaprevir exposures are increased in patients with severe hepatic impairment. Although the presence of a low dose of ritonavir in paritaprevir-containing regimens increases the likelihood of drug-drug interactions, results from several drug interaction studies demonstrated that paritaprevir-containing regimens can be coadministered with many comedications that are commonly prescribed in HCV-infected patients.

Population pharmacokinetics of paritaprevir, ombitasvir, dasabuvir, ritonavir and ribavirin in hepatitis C virus genotype 1 infection: analysis of six phase III trials

AIM

The aim of the current study was to characterize the population pharmacokinetics of a triple direct-acting antiviral (DAA) regimen (3D) (ombitasvir, paritaprevir-ritonavir and dasabuvir) and adjunctive ribavirin, and estimate covariate effects in a broad spectrum of subjects with hepatitis C virus (HCV) genotype 1 infection.

METHODS

Pharmacokinetic data from six phase III studies and one phase II study in subjects receiving the currently approved doses of the 3D ± ribavirin regimen for treating HCV genotype 1 infection for 12 weeks or 24 weeks were characterized using separate population pharmacokinetic models, built using each component of the regimen from nonlinear mixed-effects methodology in NONMEM 7.3. In the models, demographic and clinical covariates were tested. Models were assessed via goodness-of-fit plots, visual predictive checks and bootstrap evaluations.

RESULTS

The population pharmacokinetic models for each component of the 3D ± ribavirin regimen (DAAs and ritonavir, n = 2348) and ribavirin (n = 1841) adequately described their respective plasma concentration-time data. Model parameter estimates were precise and robust, and all models showed good predictive ability. Significant covariate effects associated with apparent clearance and volume of distribution included age, body weight, gender, cirrhosis, HCV subtype, opioid or antidiabetic agent use, and creatinine clearance.

CONCLUSION

The population pharmacokinetics of the 3D ± ribavirin regimen components in HCV-infected patients were characterized using phase II and III HCV clinical trial data. Although several statistically significant covariates were identified, their effects were modest and not clinically meaningful to necessitate dose adjustments for any component of the 3D regimen.

Managing drug-drug interactions with new direct-acting antiviral agents in chronic hepatitis C

Several direct-acting antiviral agents (DAAs) have marketing authorization in Europe and in the USA and have changed the landscape of hepatitis C treatment: each DAA has its own metabolism and drug-drug interactions (DDIs), and managing them is a challenge. To compile the pharmacokinetics and DDI data of the new DAA and to provide a guide for management of DDI. An indexed MEDLINE search was conducted using the keywords: DAA, hepatitis C, simeprevir, daclatasvir, ledipasvir, sofosbuvir, 3D regimen (paritaprevir/ritonavir, ombitasvir, dasabuvir), DDI and pharmacokinetics. Data were also collected from hepatology, and infectious disease and clinical pharmacology conferences abstracts. Food can play a role in the absorption of DAAs. Most of the interactions are linked to metabolism (cytochrome P450-3 A4 [CYP3A4]) or hepatic and/or intestinal transporters (organic anion-transporting polypeptide and P-glycoprotein [P-gp]). To a lesser extent other pathways can be involved such as breast cancer resistance protein transporter or UDP-glucuronosyltransferase metabolism. DDI are more likely to occur with 3D regimen, daclatasvir, simeprevir and ledipasvir, as they are all both substrates and inhibitors of P-gp and/or CYP3A4, than with sofosbuvir. They can increase concentrations of coadministered drugs and their concentrations may be influenced by P-gp or CYP3A4 inducers or inhibitors. Overdosage or low dosage can be encountered with potent inducers or inhibitors of CYP3A4 or drugs with a narrow therapeutic range. The key to interpret DDI data is a good understanding of the pharmacokinetic profiles of the drugs involved. Their ability to inhibit CYP450-3A4 and transporters (hepatic and/or intestinal) can have significant clinical consequences.

Dosing Recommendations for Concomitant Medications During 3D Anti-HCV Therapy

The development of direct-acting antiviral (DAA) agents has reinvigorated the treatment of hepatitis C virus infection. The availability of multiple DAA agents and drug combinations has enabled the transition to interferon-free therapy that is applicable to a broad range of patients. However, these DAA combinations are not without drug-drug interactions (DDIs). As every possible DDI permutation cannot be evaluated in a clinical study, guidance is needed for healthcare providers to avoid or minimize drug interaction risk. In this review, we evaluated the DDI potential of the novel three-DAA combination of ombitasvir, paritaprevir, ritonavir, and dasabuvir (the 3D regimen) with more than 200 drugs representing 19 therapeutic drug classes. Outcomes of these DDI studies were compared with the metabolism and elimination routes of prospective concomitant medications to develop mechanism-based and drug-specific guidance on interaction potential. This analysis revealed that the 3D regimen is compatible with many of the drugs that are commonly prescribed to patients with hepatitis C virus infection. Where interaction is possible, risk can be mitigated by paying careful attention to concomitant medications, adjusting drug dosage as needed, and monitoring patient response and/or clinical parameters.